Method of making electromagnetic devices



2 Sheets-Sheet 1 INVENTOR. W/ Mii/M@ Euy M, w45 D E MEGAN@ METHOD OF MAKING AN ELECTROMAGNETIC DEVICE Original Filed Sept. 2O 19 .My 6, 1946. D. E; wlEGAND METHOD OF MAKING AN ELECTROMAGNETIC DEVICE z'sheefs-sheet 2 original Filed sept. 2o, 1944 ,M EW,

Afro /vfx Patented July 16, 1946 METHOD F MAKING ELECTROMAGNETIC DEVICES David E.v Wiegand, Zanesville, Ohio, assignor to Line` Material Company, South Milwaukee, Wis., a corporation of Delaware Original application September 20, 1944, Serial No. 554,945. Divided and this application July 13, 1945, Serial No. 604,908

2 Claims. (Cl. 729-155.57)

l This invention relates to a method of making an electromagnetic device and is particularly directed to the method of making a three phase transformer.

2 through the window of the next conducting winding assembly, and with the cores free from transverse cuts or gaps thereby providing a three phase transformer which requires a low exciting This application vis a division of my prior ap- 5 current for the transformer,` and thus allowing plication, Serial No, 554,945, filed September 20, a more economical design of the three phase 1944J for Electromagnetic device and method of transformer by increasing the flux density and making the same. yet not exceeding the allowable limits of excit- Three phase transformers have heretofore been ing Current, Such methOd producing a transmade of the stacked core construction in Which former in which the path 0f the. magnetic uX a multitude of pieces of nat core steel were joined follows the grain in the magnetic ribbon due t0 together by stacking to form the necessary shape rolling, thus furthering economy by reducing core of core for the three groups of conducting Windlosses and exciting Current and allowing the meing assemblies of the three phase transformer. terial to be Workedeconomically.

This stacking operation entailed a high labor Further objects are to provide a method of cost due to the longprocess of interleaving all making a three phase transformer having three of the small pieces of steel. Even in the initial cores each of which is formed o f a plurality o stacking operation some mechanical stress was closed wound sections with two cores interlinkalways imparted to the core pieces in the pracing With a Conducting Winding assembly and Wllll tical manufacture of the transformer and this the straight leg DOI'tiOnS 0f adjacent cores arreduced the efficiency of the transformer. Also ranged with the edges of their laminations. in in the stacked core construction it is necessary the legr pOItOnS having a substantielA edge t0 for the magnetic flux to traverse a multitude of edge relatOn and J'Oinlily forming e CrileifOrIn air gaps and to travel cross grain at the corners Cross-sectional shape t0 Substantially fill the Winof the core and this entailed a certain amount dow of the conducting winding assembly, thus of loss in the core of the transformer. DlOVidng a gOOCl SlOeCe feCtOl?, the method allow- This invention is designed to overcome the ing the Winding of the conducting winding as.- above noted defects, and objects of this inven- SemblieS as Circuler CQlS With ell 0f the inherent tion are to provide a novel method of making advantages resulting therefrom such as the abila three phase transformer which has its core ity of the conducting winding to resist distorting structure formed of wound magnetic ribbon, forces due to short-circuit or Similar CendtOnS, which is wound into three closed cores each prefas the circular coil is considerably Stronger than erably composed of a plurality of sections to reetaliglllel COlS, and in additiOIl t0 lille meform cores each of which has a half cruciform Chenieal Strength entails leSS danger 0f deniegcross-section, in which no unusual care is reing the insulation during Winding than Where quired in the assembly of the parts of the device, a Teetarlgulei Conducting Winding assembly iS in which no bending, machining or other Workemployed es it requires less tension 0n the Wire ing of the core structure is required after anand n0 pOunding 0f the coil to make a firmeolhealing and which therefore results in a finished Further ObJ'eCS are t0 DIOVide a `InetllOd 0f core free from stresses, and in which short-cir- 4o making a core construction for an electromagcuiting of the laminations is avoided as the oxide netic device in which a plurality of cores for film formed on the laminations is preserved and Winding aSSenlbleS are provided and in which is not scraped oil? as there is no working subsethe cores are positioned in a regular manner with quent to annealing. their axes parallel and located at the corners of Further objects are to provide a method of a regular polygon, in which the cores are each making a three phase transformer which has formed 0f magnetic ribbon wound to provide three identical cores each having a pair of closed cores, with successive cores arranged with straight leg portions with their planes at an angle their laminations in substantial edge to edge to each other and With the straight leg portions Contact to form that portion of the core section joined by outwardly arched end portions and which receives the conducting Winding assembly with each of the three conducting winding assemand to thus facilitate the free transfer of flux blies including the primaries and secondaries surbetween adjacent portions with the minimum of rounding a straight leg portion of two of the air gaps. cores, with the cores extending from the win- In greater detail, further objects are to prodow ofone conducting winding assembly directly vide a novel method of making a three phase transformer which method contemplates the winding of three closed cores from magnetic ribbon either on a rectangular mandrel or on a circular mandrel in which latter case the cores would be subsequently given a generally rectangular shape having rounded ends, in either case providing three cores each having two straight leg portions preferably of half cruciform cross-section the clamping of the straight leg portions and rotation of such portions through a relatively small angle while they are clamped to cause the Figure l is a plan View of the transformer withy parts broken away and parts in section.

Figure 2 is a side elevation of the transformer with parts broken away and parts in section.

Figure 3 is a sectional view on the line 3--3 of Figure 4, showing, however, only a lportion .of the rst section of the core wound in place on the mandrel.

Figure 4 is a view showing how a core is wound on a mandrel, such View being partly broken away and partly in section.

Figure 5 is a side elevation of one of the cores before it is bent.

Figure 6 is a sectional view on the line 6-6 of Figure 5, showing in dot and dash lines the position that the straight legs of the core take after bending.

Figure 7 is a view showing the corer in section and clamped in bent position ready for annealing.

The method used in making this transformer is to first wind one section of a core of the narrowest magnetic ribbon onta mandrel l. This section is indicated by the reference character A. After this section has been built up to a sucient extent, the'end thereof is tack welded or brazed. and a wider section of magnetic ribbon is wound in place and is indicated by the reference character B. This wider section rests partly on the previously wound section A and also on a shouldered portion of the mandrel. Its end is tack welded or brazed. Thereafter a narrow section C is wound on the section B and its end is tack welded or brazed. The section C and the section A are of the same width. If desired, other sections could be wound in place of the three sections A, B, and C to more nearly approximate a half circle, though it has been found that two of the half cruciform shapes shown in section in Figure 4 are suicient to give a very good space factor, as will be seen from reference to Figure 1. The completed core is indicated by the reference character 2.

If desired, the mandrel may be a circular mandrel and thereafter the circular wound core may be shaped to provide two straight leg portions, as shown in Figure 5. It is preferable, however, to wind the core on a mandrel of approximately rectangular contour having rounded ends, as shown in Figure 3.

.Referring to Figure 6, it will be seen that along one side of the core all of the edges of the laminations end in a common plane. The portions shown in full lines in Figure 6 show the core as it comes from the mandrel. The dot and dash lines show the core after it has been bent so as to turn the planes of the laminations of the two straight leg portions of the core at an angle to each other. Only a 30 turn for each straight leg portion is required as shown in Figure 6.

This invention is an improvement over that disclosed in the copendng application of Arthur R. Woolfolk, Serial No. 512,134 filed November 29, 1943, for Electromagnetic device and method of making the same, for it will be seen that the angle through which the straight leg portions of the cores have to be bent in the present case is only 30, whereas in the copending application the angle through which the straight leg portions have to be bent is 60. In the copendin-g application the straight leg portions were arranged back to back, whereas as will be seen as the description proceeds this invention arranges the adjacent straight leg portions in such a manner that there is parallelism between the laminations of adjacent core sections, and in addition there is substantially an edge to edge Contact between the laminations of the adjacent core sections, thus allowing free transfer of iiux from one core sec-l tion to an adjacent core section with minimum air gaps.

After the core section is removed from the mandrel, the straight leg'portions are clamped between the members 3 and 4 and thereafter are each turned through a 30 angle allowing the end portions to arch outwardly in a smooth curve.

f After the straight leg portions have been turned through the 30 vangle as indicated, a brace 5 is bolted to the clamps so as to hold the straight leg portions with their laminations turned at an angle to each other as shown.

The core section is then annealed while it is held clamped in the position shown in Figure '7 so as to remove all stress and so as to cause it to take a set and remain in the position shown in Figure 7. After annealing the brace 5 is detached from the clamps and the clamps are removed from the straight leg portions. The core section will retain its shape after annealing.

After annealing there is no working of any sort--no bending, machining or any other type of working done on these core sections-and consequently there is no mechanical stress which would interfere with the magnetic characteristics of the core sections.

In assembling the transformer the core sections are positioned with their straight faces in contact with each other so as to secure a substantial edge to edge contact between the laminations of adjacent core sections, as shown in Figure l. After the core sections have been assembled as described and as shown in Figure 1, the conducting winding assemblies 6, see Figures 1 and 2, are

wound about the straight leg portions of adjacent core sections. These conducting winding assemblies include both the primaries and the secondaries and may be wound in any suitable manner directly on the cores.. They may be wound, for example, on the winding machine disclosed in the patent to Steinmayer et al. No. 2,305,999 of December 22, 1942, for Method and machine for winding coils, or they may be wound on the machine disclosed in the patent to Schultz et al. No. 2,334,131 of November 9, 1943, for Machine for winding coils and method of winding coils.

These winding assemblies are circular and coni sequently have all of the inherent advantages resultng therefrom such. as the ability of the conducting winding assembly to resistA distorting forces due to short-circuit or similar conditions, as circular coils are considerably stronger than rectangular coils. In addition to this-there is, less danger of damagingA the insulation during Winding than where a rectangular conducting winding-l assembly is employed as the circular winding;

requires less tension on the wire and no pound: ing on the coil to make a firm coil.

The magnetic ribbon may consist of any suitable material, such as either hot or cold rolled silicon steel. The method described is such that no sharp angles or bends are imparted to any portion of the cores and instead the rounded arched end portions connecting the straight leg portions of a core are gradually curved. This is shown most clearly in Figure 2 and it will be seen that there is no abrupt change in curvature from one portion of the arched end portions to any other portion of the arched end portions but that the change in curvature is gradual. In reality the arched end portions are somewhat conical and have their greatest curvature on their outer edges and their least curvature on their inner edges. This is a bending operation which is readily performed and does not require any special care. The arched end portions naturally form themselves as described when the straight leg portions are turned to the position shown in Figure '7.

It is to be noted from reference to Figure 1 that the axes of the three conducting windings are parallel and arranged at the apexes of an equilateral triangle. It is also to be noted particularly as set forth hereinabove that there is no sharp bending produced at the connecting arched end portions of the core sections but that the arched end portions are gradually arched and their radius of curvature varies gradually from point to point. This is an important factor in the making of a transformer as it enables the correct bending or angular positioning of the straight leg portions without unduly stressing the material at the curved and smoothly arched end portions.

It is to be noted also that due to the symmetrical arrangement of the transformer as shown most clearly in Figure l, it is possible to mount the transformer in a circular tank.

It will be seen that a novel method of producing a three phase transformer as well as a novel method of producing a core construction for a three phase transformer has been provided by this invention. In addition to this it is to be noted that the process of making the transformer may be very rapidly followed and requires a very small number of operations to produce the inal transformer.

The magnetic ribbon has a grain due to rolling which extends lengthwise of the ribbon and is most permeable to magnetic fluxv along the grain, that is to say, lengthwise of the ribbon. This invention utilizes this most permeable path as the magnetic ux is lengthwise of the ribbons in al1 of the core sections.

It is to be noted from reference to Figure 1 that there is a substantial edge to edge contact of the laminations in adjacent core sections. This construction, therefore, provides for the free transfer of flux from the straight leg portion of one `core to the straight leg portion of the adjacent core.

It is within the province of this invention to grind the at adjacent faces of the straight leg portions of adjacent core sections prior to annealing if so desired. Any wire edges that may jacent faces with an insulating paint or varnishl provided, however, that the parallel edges off thelaminations inadjacent core sections are in very-f close juxtaposition approaching closely tocanedge to edge contact. Howeven. an edge to edge contact is preferred.

It is to be noted that the ilux passing from one core section to an adjacent core section passes edgewise from the edge of one lamination into the edge of the corresponding lamination of the adjacent core section and does not have to traverse any air gaps between the at faces of laminations. In this way minimum reluctance is obtained between adjacent core sections.

Also it is to be noted that a very small exciting current is required as the magnetic ribbon forming the core sections is continuous and is not broken by cross cuts with the resulting air gaps but instead is, as stated, formed of continuous closed wound magnetic ribbon.

While the invention is primarily directed to a method of making a three phase transformer, it is to be understood that the core construction may be used for other electromagnetic devices. It is to be noted further that while three main cores and three main winding assemblies have been shown and described, it is possible to use six main cores and six main winding assemblies for a three phase transformer and to still have the axes of the cores parallel and arranged in a regular order and located at the corners of a regular polygon, and, in other types of electromagnetic devices, to use a different number of cores and winding assemblies provided the symmetry of arrangement is preserved by having the axes of the cores parallel and arranged at the corners of a regular polygon.

Although this invention has been described in considerable detail, it is to be understood that such description is intended as illustrative rather than limiting, as the invention may be variously embodied and is to be interpreted as claimed.

I claim:

1. The method of making a three phase transformer comprising forming three closed cores of wound magnetic ribbon each core having a pair of straight leg portions, clamping the .straight leg portions of each core and turning the clamped straight leg portions to place the planes of the ribbon in one straight leg portion at an angle to the planes of the ribbon in the other straight leg portion for each core and allowing the end portions to arch outwardly at each end of each core, annealing the cores while they are clamped and while the straight leg portions for each core are held in their angular relation to each other, assembling the cores with the edges of the laminations in adjacent cores arranged in a substantial edge to edge contact, and winding three conducting winding assemblies around the straight leg portions of the cores with each winding assembly surrounding a straight leg portion of each of two adjacent cores.

2. The method of making a three phase transformer comprising winding three closed cores of magnetic ribbon with each core having two straight leg portions joined by end portions and with each core formed of a plurality of sections consisting at least of a wider central section and narrow inner and outer sections, clamping the straight leg portions of each core'and turning the clamped straight leg portions to place the planes of the ribbon in one straight leg portion at an angle to the planes of the ribbon in the other straight leg portion for each core and allowing the end portions to arch outwardly at each end of each core, annealing the cores While they are clamped and While the straight leg portions for each core are held in their angular relation to each other, assembling the cores with l0 8 the leg portions of adjacent cores arranged with their laminations in substantial edge to edge contact and with the leg portions of adjacent cores forming acruciform cross-section, and winding three circular conducting winding assemblies around the straight leg portions of the cores with each conducting winding assembly surrounding a leg portion of each of two adjacent cores. f

DAVID E. WIEGAND. 

